1. Field of Invention
This invention relates to a fluid control valve and, in particular, to a gas regulator valve useful with gas fired appliances such as space heaters.
2. Brief Statement of the Prior Art
Gas supply control valves for appliances such as space heaters have operating characteristics which are closely specified by the American Gas Association. These operating characteristics have resulted in a fairly common valve design such as illustrated in U.S. Pat. Nos. 3,502,101, 3,685,732 and 3,513,873. The valves typically have a housing with inlet and outlet ports separated by a valve member carried on the diaphragm of a diaphragm actuator with the opening side of the diaphragm pressured with the gas pressure of a bleed chamber within the housing. The bleed chamber receives the supply gas through a bleed orifice and communicates with the exit port through a first, snap-acting, heating-demand valve and a second, pressure regulator valve. The latter has a diaphragm valve actuator and responds to the gas pressure in the exit port of the valve.
The aforedescribed valve structure has a snap opening characteristic and is either off or on, supplying gas at a predetermined, controlled supply pressure. It is desirable, however, to provide a throttled or reduced pressure gas supply upon initial opening of the valve. This is desirable to establish heated convection currents in the flue of the appliance before the appliance burner is fully on, thereby avoiding the possibility of flame rollout or other difficulties maintaining combustion of the burner. Some valves have been proposed having a stepped opening characteristic in the gas supply pressure, however, the time interval between the stepped opening of the valves is variable, depending to a substantial extent on the inlet gas pressure to the valve.